EF多表查询方式

5， 连接

可以的连接有Join 和 GroupJoin 方法。GroupJoin组联接等效于左外部联接，它返回第一个（左侧）数据源的每个元素（即使其他数据源中没有关联元素）。

using (var edm = new NorthwindEntities())

    {

       var query = from d in edm.Order_Details

                   join order in edm.Orders

                   on d.OrderID equals order.OrderID

                   select new

                    {

                        OrderId = order.OrderID,

                        ProductId = d.ProductID,

                        UnitPrice = d.UnitPrice

                     };

        foreach (var q in query)

         Console.WriteLine("{0},{1},{2}",q.OrderId,q.ProductId,q.UnitPrice);

}

参考资料：

http://blog.csdn.net/niewq/article/details/42718515